There is known a configuration in a chair, for example, in which a surface contacting a human body of a seater in a seated state, i.e., a backrest surface of a backrest or a seat surface of a seat body supporting the human body is formed by stretching an upholstery fabric formed by an elastic cloth of which a ground texture is composed by knitting or weaving in a mesh shape (for example, see Patent Literatures 1 and 2).
Such an upholstery fabric may obtain seating comfort and appropriate breathability, for example, when a backward curved amount caused by a load of a human body when a seater leans against the backrest is set to be large at the upper portion supporting an upper portion of a back compared to the lower portion supporting a lower portion of the back.
However, in the backrest of the chair disclosed in Patent Literature 1, since the meshed upholstery fabric having a uniform density as a whole is stretched over the rim-shaped backrest frame, when the lower portion of the upholstery fabric is set to an appropriate curved amount, the upper portion is curved backward too much. On the contrary, when the upper portion of the upholstery fabric is set to an appropriate curved amount, the lower portion is curved too much. Due to these problems, the seating comfort may not be obtained in any case.
Further, in the backrest disclosed in Patent Literature 2, on the entire surface of the clothing fabric constituting the upholstery fabric (the backrest seat body), band-shaped meshed portions (low elastic portions) in the left and right direction and the clothing fabrics are alternately arranged in the up and down direction, i.e., woven in a plurality of steps in the up and down direction. Thus, the entire curved amount of the upholstery fabric is substantially uniform, and the seating comfort may not be improved by setting the backward curved amount of the upper portion to be larger than that of the lower portion.
Furthermore, the upholstery fabric is formed by composing long yarns in a mesh shape, and the elastic deformation force thereof is uniform in any portion of the entire surface of the cloth. For this reason, when the upholstery fabric is applied to, for example, the backrest surface of the backrest and the seat surface of the seat body of the chair, a desirable sensation of seating in response to the respective portions of the human body may not be obtained because the support strengths required for the loads of the back of the seater, the seated portion, and the leg contact portion are different from each other.
In order to solve such problems, there is known a chair, which has been filed by the present applicant and published already, in which an upholstery fabric of a backrest applies a strong elastic resistance to a seater's waist portion where a strong support force is required (Patent Literature 3).
In the upholstery fabric which is stretched over the backrest of the chair disclosed in Patent Literature 3, the elastic cloth is completely divided into two parts, i.e., a meshed ground texture and a fascia portion denser than the ground texture. The fascia portion is used for a portion corresponding to the seater's waist portion where a strong support force is required, and the ground texture is used for the other portions.